// Copyright(c) 2015-present, Gabi Melman & spdlog contributors.
// Distributed under the MIT License (http://opensource.org/licenses/MIT)
#pragma once

#include <chrono>
#include <iterator>
#include <spdlog/common.h>
#include <spdlog/fmt/fmt.h>
#include <type_traits>

#ifdef SPDLOG_USE_STD_FORMAT
#include <charconv>
#include <limits>
#endif

// Some fmt helpers to efficiently format and pad ints and strings
namespace spdlog {
namespace details {
    namespace fmt_helper {

        inline void append_string_view(spdlog::string_view_t view, memory_buf_t& dest)
        {
            auto* buf_ptr = view.data();
            dest.append(buf_ptr, buf_ptr + view.size());
        }

#ifdef SPDLOG_USE_STD_FORMAT
        template <typename T> inline void append_int(T n, memory_buf_t& dest)
        {
            // Buffer should be large enough to hold all digits (digits10 + 1) and a sign
            SPDLOG_CONSTEXPR const auto BUF_SIZE = std::numeric_limits<T>::digits10 + 2;
            char buf[BUF_SIZE];

            auto [ptr, ec] = std::to_chars(buf, buf + BUF_SIZE, n, 10);
            if (ec == std::errc())
            {
                dest.append(buf, ptr);
            }
            else
            {
                throw_spdlog_ex("Failed to format int", static_cast<int>(ec));
            }
        }
#else
        template <typename T> inline void append_int(T n, memory_buf_t& dest)
        {
            fmt::format_int i(n);
            dest.append(i.data(), i.data() + i.size());
        }
#endif

        template <typename T> SPDLOG_CONSTEXPR_FUNC unsigned int count_digits_fallback(T n)
        {
            // taken from fmt: https://github.com/fmtlib/fmt/blob/8.0.1/include/fmt/format.h#L899-L912
            unsigned int count = 1;
            for (;;)
            {
                // Integer division is slow so do it for a group of four digits instead
                // of for every digit. The idea comes from the talk by Alexandrescu
                // "Three Optimization Tips for C++". See speed-test for a comparison.
                if (n < 10)
                    return count;
                if (n < 100)
                    return count + 1;
                if (n < 1000)
                    return count + 2;
                if (n < 10000)
                    return count + 3;
                n /= 10000u;
                count += 4;
            }
        }

        template <typename T> inline unsigned int count_digits(T n)
        {
            using count_type = typename std::conditional<(sizeof(T) > sizeof(uint32_t)), uint64_t, uint32_t>::type;
#ifdef SPDLOG_USE_STD_FORMAT
            return count_digits_fallback(static_cast<count_type>(n));
#else
            return static_cast<unsigned int>(fmt::
// fmt 7.0.0 renamed the internal namespace to detail.
// See: https://github.com/fmtlib/fmt/issues/1538
#if FMT_VERSION < 70000
                                                 internal
#else
                                                 detail
#endif
                                             ::count_digits(static_cast<count_type>(n)));
#endif
        }

        inline void pad2(int n, memory_buf_t& dest)
        {
            if (n >= 0 && n < 100)  // 0-99
            {
                dest.push_back(static_cast<char>('0' + n / 10));
                dest.push_back(static_cast<char>('0' + n % 10));
            }
            else  // unlikely, but just in case, let fmt deal with it
            {
                fmt_lib::format_to(std::back_inserter(dest), SPDLOG_FMT_STRING("{:02}"), n);
            }
        }

        template <typename T> inline void pad_uint(T n, unsigned int width, memory_buf_t& dest)
        {
            static_assert(std::is_unsigned<T>::value, "pad_uint must get unsigned T");
            for (auto digits = count_digits(n); digits < width; digits++) { dest.push_back('0'); }
            append_int(n, dest);
        }

        template <typename T> inline void pad3(T n, memory_buf_t& dest)
        {
            static_assert(std::is_unsigned<T>::value, "pad3 must get unsigned T");
            if (n < 1000)
            {
                dest.push_back(static_cast<char>(n / 100 + '0'));
                n = n % 100;
                dest.push_back(static_cast<char>((n / 10) + '0'));
                dest.push_back(static_cast<char>((n % 10) + '0'));
            }
            else
            {
                append_int(n, dest);
            }
        }

        template <typename T> inline void pad6(T n, memory_buf_t& dest) { pad_uint(n, 6, dest); }

        template <typename T> inline void pad9(T n, memory_buf_t& dest) { pad_uint(n, 9, dest); }

        // return fraction of a second of the given time_point.
        // e.g.
        // fraction<std::milliseconds>(tp) -> will return the millis part of the second
        template <typename ToDuration> inline ToDuration time_fraction(log_clock::time_point tp)
        {
            using std::chrono::duration_cast;
            using std::chrono::seconds;
            auto duration = tp.time_since_epoch();
            auto secs = duration_cast<seconds>(duration);
            return duration_cast<ToDuration>(duration) - duration_cast<ToDuration>(secs);
        }

    }  // namespace fmt_helper
}  // namespace details
}  // namespace spdlog
